Honors Program Theses


Open Access Honors Program Thesis

First Advisor

Kavita R. Dhanwada


Atrazine is the second most-commonly applied herbicide in the United States. Studies have correlated herbicide exposure with a variety of health risks in non-target organisms, including humans and amphibians. Previous work from our laboratory has shown that low-level atrazine exposure inhibits cell growth and may delay progression through the cell cycle.

The purpose of the current study is to determine the effect of environmentally-relevant levels of atrazine on the expression of cyclin D 1, a protein that regulates the G 1 phase of the cell cycle. HepG2 human liver cells were exposed to increasing levels of atrazine (0, 50, 100, 300 parts per billion, ppb) for 24 or 48 hours. Cyclin D1 expression was quantitated by Western blot analysis in atrazine-treated and control cells. Results showed decreased expression of cyclin D1 in atrazine-treated cells compared to control cells.

Timecourse experiments were conducted using synchronized HepG2 cells. Cells, treated with 300 ppb atrazine or left untreated (control), were harvested at specific time points within the cell cycle (1, 4, 8, 12, 24, 48 hours). Western blot analysis was then used to measure relative cyclin D1 protein expression at each time point. Results indicate that atrazine-treated cells exhibit decreased cyclin D1 expression at the 48 hour time point compared to control cells. Together, these observations suggest that atrazine exposure induces a G 1 block in the cell cycle.

A series of experiments was also designed to measure levels of cyclin D 1 mRNA production within atrazine-treated human HepG2 cells. Real-time PCR analysis was used to measure mRNA transcripts specific to cyclin Dl. Preliminary results suggest decreased levels of cyclin Dl mRNA production in atrazine-treated cells compared to control, but more experiments are required to confirm this result.

Year of Submission



Department of Biology

University Honors Designation

A thesis submitted in partial fulfillment of the requirements for the designation University Honors


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Date Original


Object Description

1 PDF file (vii, 44 pages)